Vertebrae and caudal fin skeleton.
30–31 total vertebrae (excluding urostyle element), with 14–15 abdominal and 16–17 caudal vertebrae. Pterygiophore supporting last dorsal-fin spine is inserted between neural spines of 15th and 16h, 16th and 17th, or 17th and 18th vertebra (counted from anterior to posterior). Pterygiophore supporting last anal-fin spine is inserted between haemal spines of 15th and 16 th vertebra or 16th and 17th vertebra. Single predorsal bone (=supraneural) present. Hypurals 1 and 2 as well as hypurals 3 and 4 always fused.
Colouration in life (based on field photographs of adult specimens).
(
Fig. 4
) Body ground colouration pale brown to yellowish. Dark grey to brownish, interrupted midlateral band extending from operculum to just behind caudal fin base ending as a blotch (less distinct than in
O. luongoensis
and sometimes hardly visible at all); midlateral band intensity varies depending on mood, sometimes fainting to greyish band. Midlateral band crossed by 7–10 light brown to sooty black vertical bars; these bars are short (extending shortly above and below midlateral band) and rather faint in colouration and not always recognizable. However, it should be mentioned that intensity of body markings is strongly dependent on motivational state. Chest light beige with some reddish sparkles (especially in bigger specimens). Belly light beige. Dorsal head surface and snout pale brown to greyish; cheek beige to yellow-greyish. Iris reddish at level of interorbital stripe/anterior extension of midlateral band (red more prominent in bigger specimens). Lower jaw and mental area pale beige to reddish. Throat and branchiostegal membrane reddish (ventral side of branchiostegal membrane in
O. luongoensis
blackish). Operculum beige to yellow-greyish with a dark grey to blackish opercular spot connecting anterior extension of midlateral band that ends almost at posterior edge of eye. Another light brownish element of variable form and intensity on ventral corner of operculum; such element also present in
O. luongoensis
but less intense in
H. katumbii
. Dark grey to brownish lachrymal stripe ending at posterior end of upper lip. Thin, dark grey to brownish nostril stripe (sometimes interrupted) in form of flattened
U
extending between nostrils. Dark grey to brownish interorbital stripe more intense than nostril stripe. No supraorbital stripe present. Upper and lower lip beige to pale brown, lower margin of upper lip greyish, lower lip lighter then upper lip. Dorsal fin membrane light orange to pale brown with columns of light reddish-orange to brownish maculae between branched rays and to some degree between last dorsal-fin spine (membrane between maculae brighter, almost hyaline); spinous dorsal fin with black marginal band and reddish-orange lappets; marginal band extending to some degree onto rayed part of dorsal fin. Anal fin light orange to pale brown, more intensively coloured towards distal margin. Spinous anal fin with faint reddishorange margin. No maculae or eggspots present. Caudal fin light orange to pale brown becoming more intensively coloured near margin; membrane between rays with three vertical columns of small greyish maculae (membrane between maculae brighter, almost hyaline, especially in central part of caudal fin). Outer caudal-fin rays with dark orange to blackish margin. Pectoral fin light orange, especially rays of this colour. Pelvic fin compared to pectoral fin less coloured, appearing almost transparent, membrane of pelvic fin spine greyish.
Juvenile colouration in life.
(based on photos of tank-raised juveniles approximately
25 mm
SL;
Fig. 9
) Ground colouration greyish, belly beige. Patterns and stripes of head as described for adults. Greyish vertical bars on flanks more prominent than in adults. Iris greyish. Dorsal fin hyaline with some blackish spots on membrane; all other fins hyaline.
Colouration in alcohol.
Colouration and melanin patterns similar to live specimens, but due the preservation procedure of specimens, i.e., first formalin fixation, transfer to 75 % EtOH etc., specimens tend to lose original colouration (especially melanin patterns more intense than in live specimens). Overall body ground colouration brownish; dorsum, flank and caudal peduncle brownish becoming beige at ventral side (band of one to two scales ventrally of flanks and caudal peduncle). Chest beige to light brownish and belly beige. Branchiostegal membrane light greyish, ventral side of branchiostegal membrane dark brown, towards anterior tip becoming brighter. Dorsal head surface brownish as dorsum, ethmoidal area becoming greyish-brown. Upper lip light greyish to beige; lower margin of upper lip greyish; lower lip beige. Cheek beige to brownish; centrally below eye a brownish blotch of variable intensity visible (as in
O. luongoensis
, which is not the case in living specimens). Operculum brown to dark brownish with opercular spot as described above; light brownish element of living specimens hardly visible or indistinguishable from operculum ground colouration in conserved specimens. Markings of head mask dark brownish to dark grey. Midlateral band dark brownish and vertical bars light brownish (less distinct than midlateral band). Dorsal fin greyish with black margin, subsequently followed by beige lappets; greyish maculae mainly on rayed part still visible but less intense. Anal fin whitish to beige. Pectoral fin beige. Pelvic fin beige; membrane of spine light greyish. Caudal fin light, at base pale brownish, caudally becoming beige; greyish maculae still present but less intense; margins blackish.
Distribution and biology.Orthochromis katumbii
is known from Kiswishi River, a western tributary of the
Luapula
and from the Mambilima Falls on the
Luapula
(
Fig. 1
). At the
type
, locality the Kiswishi River is about ten meters wide and on average about one meter deep and the bottom substrate consists of gravel and smaller rocks (
Fig. 8
). Water temperature varied between 19.3 and 23.8 °C (measured in August and September), pH between 7.73–7.95, electrical conductivity 377.7 and 380.1µS.
O. katumbii
is a benthic-rheophilic maternal mouthbrooder with clutch sizes, in captivity, of between 25 and
30 eggs
(pers. comm. J. Geck). Recently a monogenean gill parasite
Cichlidogyrus consobriniJorissen, Pariselle and Vanhove 2017
was described from specimens obtained from
O. katumbii
and
Sargochromis mellandi
(
Boulenger 1905
)
.
Etymology.
The species is named after Mr. Moïse Katumbi who supported part of the 2015 ichthyological research field expedition of the Mbisa
Congo
project in
Katanga province
of the
DRC
, who himself is a great fish enthusiast. Some specimens of the new species were collected on his farm “Ferme de Futuka”.